In recent years, an electric connection box using a metal core board which is excellent in heat radiation has been proposed in response to various requirements in the field of motorcar such as miniaturization, increase in the amount of electric current used, simplification of design change and so on.
The metal core board is a printed circuit board having at least one internal metal core which is made of metal such as copper or aluminum.
Generally, the soaking in the metal core board is improved as the thickness of the metal core board increases. On the other hand, the electric connection box for motorcar is requested to be formed as thin as possible for providing the soaking effect to the board while reinforcing the board since its weight and strength can be concerned.
In the past, there have been proposed various techniques for reinforcing printed circuit boards used in the electric connection boxes.
For example, Japanese Laid-Open Patent Publication No. 2001-237572 discloses a reinforcing structure in which a printed circuit board is supported on a support member in a housing through a reinforcing member (which will be referred to as the related art 1).
Japanese Laid-Open Patent Publication No. 2004-72881 discloses a structure in which a heat radiating plate is sandwiched between two metal core boards (which will be referred to as the related art 2).
Japanese Laid-Open Patent Publication Hei 7-321421 discloses a structure in which a reinforcing material is applied to a flexible printed circuit board (which will be referred to as the related art 3).
There is furthermore need for installing more boards in an electric connection box in response to the increased number of electrical and electronic parts in the motorcar.
However, the electric connection box according to the related art comprises a metal core board disposed horizontally relative to an upper or lower casing portion by fastening it to the casing through screws or the like at the corners of the board (at four corners in a square board) so that the desired strength of the metal core board is secured. In such a case, the total number of two boards, one on the upper casing portion and one on the lower casing portion, can be disposed in the electric connection box at the best. This technique will be referred to as the related art 4.
Patent Document 1:
Japanese Laid-Open Patent Publication No. 2001-237572 bulletin
Patent Document 2:
Japanese Laid-Open Patent Publication No. 2004-72881 bulletin
Patent Document 3:
Japanese Laid-Open Patent Publication Hei 7-321421 bulletin
The related art 1 raises a problem in that the size of the device is increased in a direction perpendicular to the plane of the printed circuit board since the reinforcing members are attached to the printed circuit board at the opposite ends thereof.
The related art 2 raises another problem in that it is difficult to reduce the weight of the reinforcing structure since the metallic heat radiating plate itself is heavy.
The related art 2 raises still another problem in that the connections for connecting the heat radiating plate to a vehicle body or the like extend outwardly from the main body of the heat radiating plate. This is disadvantageous to reduction of the size.
The related art 3 raises a further problem in that the heat radiation in the flexible printed circuit board cannot be secured since the flexible printed circuit board is applied to the reinforcing member.
The related art 4 raises a further problem in that the number of boards which can be disposed in the casing is limited since the board is disposed horizontally relative to the casing.
Therefore, the space within the casing cannot be used effectively.